Roll stand

ABSTRACT

The roll stand comprises a frame with pads housing one drive working roll connected to a drive and adapted to deform a bar being rolled, and idle rolls connected to drives to be accelerated and to synchronize the rates of rotation thereof with that of the drive working roll. The drives designed to accelerate and synchronize idle rolls are fashioned as combined flange-type non-contact electric motors having armatures which are mounted on the axles of idle rolls, and the stator windings are mounted in the pads of the roll stand, the stator windings of the drives being connected to a.c. supply sources. The present invention has as its objective to increase the speed of rolling of the stand and decrease of its over-all dimensions and weight.

United States Patent [19] Borisenko et al.

[ ROLL STAND [76] Inventors: Gleb Pavlovich Borisenko, ploschad Oktyabrskaya, 7, kv. 28; Jury Sergeevich Chernobrivenko, ulitsa Dzerzhinskogo, l6, kv. 7; Jury Kutsov, ulitsa Kirova 8, kv. 9; Arkady Alexeevich Gorbanev, ulitsa Serova 1a, kv. 4; Oleg Nikolaevich Kukushkin, ulitsa Suvorova l3, kv. 21; Vladimir Nikolaevich Krivobokov, ulitsa G. Pushkina; Grigory Gavrilovich Pobegailo, pereulok Uritskogo, l l, kv. 3;- Vitaly Dmitrievich Nashivanko, ulitsa G. Pushkina, lb, kv. 57, all of Dnepropetrovsk, U.S.S.R.

22 Filed: June-11,1973" 21 Appl. No.: 368,575

52 u.s.c|. 72/249, 72/19 51 Int. c1 ..B21b35/00 58 Field of Search ..72/249, 19,29

[56] References Cited UNITED STATES PATENTS Bretschneider 72/249 Aug. 13, 1974 Primary ExaminerMilton S. Mehr Attorney, Agent, or Firm-Holman & Stern [5 7] ABSTRACT The roll stand comprises a frame with pads housing one drive working roll connected to a drive and adapted to deform a bar being rolled, and idle rolls connected to drives to be accelerated and to synchronize the rates of rotation thereof with that of the drive working roll. The drives designed to accelerate and synchronize idle rolls are fashioned as combined flange-type non-contact electric motors having armatures which are mounted on the axles of idle rolls, and the stator windings are mounted in the pads of the roll stand, the stator windings of the drives being connected to ac. supply sources. The present invention has as its objective to increase the speed of rolling of the stand and decrease of its over-all dimensions and weight.

7 Claims, 4 Drawing Figures PATENIEUAUB 1 3m 3.828.600

SHEET 1 [IF 3 PATENTEI] AUG 1 3 I974 SHEET 3 BF 3 ROLL STAND BACKGROUND oF THE INVENTION The present invention relates generally to metal rolling and more particularly, it relates to roll stands of a block-structure mill for rolling solid and hollow metal bars.

Presently, use is made of roll stands having preferably two or three rolls.

ln double-roll stands the rolls are positioned at an angle of 45 with respect to the horizontal plane, whereas each pair of the rolls in the stands of a mill is disposed at an angle of 90 relative to the pair of the rolls of the adjacent stand.

In three-roll stands all the rolls are positioned'at an angle of 120 relative to one another, whereas each stand of the rolling mill is turned about the rolling axis at an angle of 60 relative to the adjacent stand.

In the conventional double-roll stand, the rolls are rotated by an electric motor through a transmission reduction gear andan intermediate transmission. The pair of the rolls is rotated through a system of rack hyperbolic gears.

The above double-roll stand mounted on the body of the main reduction gear is, just alike the working stand, of no independent significance, and should be considered alongside with the design of the reduction gear of the main drive adapted to simultaneously transfer torque to a number of analogous stands assembled into a block.

Employment in the main drive of the stand of precision gearings in combination with oblique-toothed gear rolls has made it possible to dispense with clutches and spindles in the drive and, therefore, to raise the rate of rolling up to 50 m/sec.

The technological process of rolling carried out at high rates requires higher accuracy of manufacture of gearings of the reduction gear and, for this reason, the gearings of the main drive of the stand are manufactured in accordance with 11-12 precision grade, which corresponds to the precision of manufacture as used in aviation machine-building.

In spite of the positive technological and constructional features, the conventional double-roller stand has the following disadvantages.

lncrease of the rolling rate in the stand has resulted in development of additional measures aimed at improvement of dynamic characteristics of the stand, for instance, installation of vibration dampers in the main reduction gear, which has made the design of the stand still more complicated.

The design of the reduction gear of the main drive of the stand is extremely intricate, it has a great weight and requires employment of high grades of manufacture precision, which raises the production costs of certain units of the stand by several times.

A double-roll stand is also known having rolls which are rotated by a controlled electric motor through a common reduction gear reduction gears specially provided for each stand, aligned with gear stands and disposed along the frame of the block of stands, and drive spindles equipped with Hook's joints.

The main disadvantage of the stand lies in the complex design of the main drive. The bulky equipment to be found in the main drive of the stand considerably enlarges the over-all dimensions of the block of stands and its weight.

Moreover, as it has been experimentally proved, employment of spindles with Hooks joints in the main drive brings about considerable vibration in the rolling axles and, consequently, to the rolls that are mounted cantileverly on the axles. [n such cases the amplitude of rolls vibration sometimes reaches values resulting in distortion of the allowances of articles being rolled.

Presence of considerable mechanical vibration in the stands of this type affects not only the geometrical dimensions of the articles being rolled, but also the stability of the stand bearing units by considerably reducing A design of a three-roll roll stand is also known in the art having one input shaft and internal distribution of rotation with the aid of bevel gearings, and used mainly for rolling bars made from carbon and low-alloy steel. The minimal diameter of rolls of such stands is 250 mm, and the maximal rate of bar rolling in such stands is 45 m/sec.

Diverse variants of bevel gearings are made use of in the stands of this design. The rolls in such stands may bemounted either on rotating or non-rotating axles.

Among the disadvantages of this design of a threeroll stand is that disposed inside the stand are bevel gearings which should be precision-made to provide operation at high rates. Further, in the case of internal distribution of rotation the supporting power of the bearing units and bevel gearings, as compared to that of double-roller stands, is smaller as in three-roll stands the dimensions of bearing units and bevel gearings are limited by similar butt ends of adjacent rolls and their intersecting axles.

A design of a three-roll roll stand is known which has a powerful drive connected to only one working roller and two idle rolls.

This design eliminates a number of disadvantages of three-roll stands, but, at the same time, has some other disadvantages inherent thereto.

As compared to the afore-described one, in the stand of this design the angle of gripping is by three times smaller, which has a negative effect on the possibility of further increasing the rate of rolling.

During an interval in the mill operation, the nondriven rolls slow down the rate of their rotation, which results in disagreement of rotation of the rolls in the stand. With the rolling operation resumed, additional dynamic loads arise in the stand when the bar is being gripped.

Additionally, wear-out of the rolls in the stand is greater.

A design of a three-roll roll stand is known in the art having a powerful drive connected to only one roll and a special auxiliary drive for the other two rolls that are rigidly mechanically engaged neither with the drive roll, nor with each other. The special auxiliary drive of the two rolls is essentially boxes stationary mounted on the frame pads having wheels of small turbines seated on axles insidethereof. A jet of liquid is thrown at a high speed from a nozzle mounted on the box body in the direction tangential to the turbine wheel, and rotates the latter (cf. U.S. Pat. No. 3,611,777; CL. 72249, Oct. 1971).

A disadvantage of this design of the stand lies in that it has no members synchronizing the rates of rotation of the auxiliary rolls and the drive roll, which hampers 3 I operation of the roll stand and the block of stands of the rolling mill at high speed.

Designs of four-roll roll stand are known at present,

but are rather seldom used. Among the disadvantages of these stands are intricacy of their design and low strength.

SUMMARY OF THE INVENTION It is an object of the present invention to provide such a block-structure rollstand that will allow carrying out the rolling process at a speed of 80 m/sec and higher, which will considerably raise efficiency of the rolling mill.

Another object of the present invention is to provide such a roll stand that will make it possible to decrease the over-all dimensions and weight of the stand equipment.

Still another object of the present invention is to provide a roll stand that will allow elimination of impact loads and vibration in the stand.

Yet another object of the present invention is to simplify the design of the stand and, consequently, to reduce the costs of the equipment maintenance.

The above-mentioned and other objects are accomplished by the provision of roll stand of a blockstructure rolling mill for rolling solid and hollow metal bars, the roll stand comprising a frame with pads having bearing units mounted therein, supporting axles with a working roll and at least one idle roll, a drive for deforming a bar being rolled, the drive being connected to the working roll, and drives of idle rolls.

The roll stand of a block-structure mill adapted to roll solid and hollow metal bars comprises a frame with pads having bearing units mounted therein and carrying axles with a working roll and at least one idle rolls, a drive for deforming the bar being rolled, the drive being connected to the working roll,'and drives of idle rolls. In accordance with the present invention, each of the drives of the idle rolls is made as a combined noncontact flange-type electric motor adapted to accelerate and synchronize the rates of rotation of the working roll and the idle roll, the armature of the electric motor being mounted on the axle of the idle roll, and the stator being essentially a winding built in the pad of the roll stand and disposed in the plane parallel to the plane of rotation of the roll, the stator windings of the drives being connected to an a.c. supply source.

It is expedient to use printed windings as the stator windings, which allows to considerably decrease the size of the stator windings, to increase reliability of their operation and to prolong their service life.

It is also expedient to mount the armature of the noncontact electric motor on the butt face of the idle roll, facing the butt face of the pad mounting the stator winding.

This will make it possible to decrease the dimensions of the parts of the idle roll unit and, consequently, the overall dimensions of the stand, and to make rigid the structureof the unit, that can be easily dynamically balanced.

It is no less important to mount the stator winding on the pad face that is external relative to the idle roll, and to install the armature on the end portion of the axle of the roll in opposition to the stator winding which will ensure a quicker adjustment of the gap between the surface of the stator winding and that of the armature due to presence of free access to controllable parts of the stand.

In order to raise the accuracy of synchronization of the rates of rotation of idle rolls and the working one, it is feasible to install electric pick-ups of the rate of rotation on the axles of the idle rolls, the pick-ups being cut in electric circuits of comparison of the rates of rotation of the working roll and each idle roll, the circuits being electrically connected to a supply source so that in case the rate of rotation of the idle roll deviates from that of the working one, the frequency of the a.c. of the supply source is changed accordingly to alter the rate of rotation of the idle roll.

It is also feasible to make the idle rolls as hollow rolls housing the bearing units, and make the axles of the rolls non-rotatable, which will considerably simplify treatment of the frame of the stand and dynamic balancing of the roll.

In order to synchronize the rates of rotation of the idle rolls and the working roll, it is possible to install non-contact pick-ups in such a manner that one portion of the pick-up will be disposed on the butt face of the hollow roll with the non-rotatable axle and will face the other portion of the pick-up, mounted on the butt face of the pad.

As a result of the present invention, there has been provided a roll stand which allows to carry out the rolling process at a speed of m/sec and more, which considerably raises efficiency of the rolling mill; to decrease the over-all dimensions and weight of the stand equipment; todo away with impact loads and vibration in the stand; to simplify the design of the stand and, consequently, to reduce the costs of the equipment maintenance.

BRIEF DESCRIPTION OF THE DRAWINGS The following description of exemplary embodiments of the present invention is given with reference to the accompanying drawings, in which:

FIG. 1 shows a block-structure rolling mill for rolling metal bars, comprising a roll stand made in accordance with the present invention, a top view;

FIG. 2 shows a roll stand made in accordance with the present invention, in which the armature of a noncontact electric motor is mounted on the butt face of the idle roll, facing the butt face of the pad, mounting the stator winding, and the bearing units are disposed asymmetrically relative to the roll whose axle is made rotatable, a view taken along the axis of the rolling process, with partial extraction;

FIG. 3 shows a variant of embodiment of unit A in FIG. 2, in which the armature of a non-contact electric motor is mounted on the butt face of the hollow idle roll housing the bearing unit built therein, the axle of the roll being made not rotatable; and

FIG. 4 shows a variant of embodiment of unit A in FIG. 2, in which the stator winding is disposed on the side of pad that is external relative to the idle roll, and the armature is mounted on the end portion of the axle of the roll, the axle being made rotatable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, the block-structure rolling mill comprises a general controllable electric drive 1 connected through a clutch 2 to a group reducing gear 3 of the mill, a frame 4 of a block of stands, mounting roll stands 5, output shafts 6 of the reducing gear and electric pick-ups of the rates of rotation of the output shafts 6 of the stands 5. The pick-ups 7 are mounted on the shanks (not shown in the drawings) of the output shafts 6 of the reducing gear 3 at its side opposite to that on which the roll stands 5 are disposed.

The roll stand 5 (FIG. 2) according to the invention comprises a frame 8 with pads 9, 10 and 11 made integral therewith and accomodating a working roll 12 mounted on a drive shaft 13 and two similar idle rolls 14 and 15.

Each of the pads 9 and 10 of the idle rolls l4 and 15 has detachable universal stator units 16 mounted therein and accomodating stator windings 17 that are essentially printed ones.

The stator unit 16 has an annular cooling chamber 18 designed to cool down the stator winding 17 in the course of its operation. The cooling chamber 18 has two holes 19 adapted to supply and drain the cooling liquid, one of the holes being shown in FIG. 2.

The stator unit 16 and the stator winding 17 are installed in the body of the pad 10, and are disposed in a plane parallel to the plane of rotation of the roll 15.

The idle roll 15 is mounted on a rotatable axle 20 resting on bearing units 21 and 22 which are disposed symmetrically relative to the idle roll, the bearing unit 21 being spaced at the side of the stator unit 16 from the roll 15 over a greater distance than the bearing unit 22. The difference in the distances is determined mainly by the width of the stator unit 16.

Mounted on the butt face of the idle roll 15, facing the butt face of the pad 10 mounting the stator winding 17 is a casing 23 of the armature, the casing 23 having the armature 24 mounted therein. The armature casing 23 is secured to the body of the roll 15 with the aid of several screws 25.

In the body of the pad 10, provision is made for a duct 26 along which dried compressed air is supplied, the latter, on getting into an annular duct 27 formed by the surface of the axle 20 and the inner surface of the round hole of the stator unit 16, and a gap 28 formed by the surface of the stator winding 17 and the surface of the armature casing 23 cooling down the butt face of the stator winding 17.

Mounted on the butt end of the rotatable axle 20 is a shaft 29 of an electric pick-up 30 measuring the rate of rotation of the idle roll 15, the pick-up being cut in an electric circuit (not shown in the drawing) synchronizing the rates of rotation of the roll 15 and the working roll 12 rotated by the output shaft 6 of the reducing gear and the drive shaft 13 carrying the working roll 12.

In a manner analogous to that of the electric pick-up 30 of the idle roll 15, the second idle roll 14 mounts a similar pick-up 31 adapted to measure its rate of rotation and also cut in an electric circuit (not shown in the drawing) synchronizing the rates of rotation of the rolls l2 and 14.

Combining parts of the flange-type non-contact electric motor with parts ofthe roll stand (the stator winding 17 of the electric motor is combined with the pad 10 and is mounted therein, while the armature 24 of the electric motor is combined with the idle roll 15 and is mounted inside the latter) makes it possible to decrease the over-all dimensions of unit A in FIG. 1, and, consequently, the over-all dimensions of the roll stand.

Combining the flange-type non-contact electric motor with parts of the roll stand allows to provide an extremely compact and rigid structure of the roll stand, dynamic balancing of the idle roll 15 presenting no difficulty.

The fact that the printed windings 17 connected to an ac. supply source (not shown in the drawing) are used as the stator windings allows for decreasing the over-all dimensions of the stator unit 16 installed in the pad 10 of the roll stand 5, which, in its turn, makes it possible to decrease the dimensions of the pad and, consequently, that of the roll stand as a whole. Further, use of printed stator windings instead of windings made from wire considerably simplifies electric insulation of the winding, to raise by several times its resistance to water, and to protect it reliably against water, scale, oil and mechanical damage.

The above advantages of printed stator windings provide for considerable increase of reliability of their operation and of their service life.

The variant of embodiment of the roll stand with unit A shown in FIG. 3 has some specific features which make it a little different from the viewpoint of its design from the roll stand as shown in FIG. 2, the difference residing in the following.

Instead of the roll 15 use is made of a hollow roll 32, whereas the rotatable axle 20 having the roll 15 stationary mounted thereon and rotating together with the axle is substituted by a non-rotatable axle 33.

The bearing units 21 and 22 are substituted by one bearing unit 34, mounted inside the hollow roll 32. The design of the armature casing 23 is different too, and it now serves also as a cover 35 of the bearing unit 34, secured to the butt face of the rotatable hollow roll 32 with the aid of screws 36. Mounted at the opposite side of the bearing unit 34 on the butt face of the rotatable roll 32 is a second cover 37 of the unit, the cover 37 being fixed with the help of screws 38.

In order to cool down the butt face of the stator winding 17, facing the gap 28, compressed air is supplied along a duct 39 made in'he body of the non-rotatable axle 33, and ducts 40 disposed perpendicularly to the duct 39 and along the radii of the axle 33.

In this variant of embodiment of the roll stand, in order to synchronize the rates of rotation of the idle rolls 14 and 15 with that of the working roll 2, provision is made for non-contact pick-ups, one portion of the pick-up being mounted on the butt face of the hollow roll 32 with the non-rotatable axle 33 and facing the other portion of the pick-up, mounted on the butt face of the pad 11 of the roll.

Used as the portion of the non-contact pick-up, mounted on the butt face of the hollow roll 32 is one of the screws 38 whose head 41 somewhat projects into the gap between the butt end of the roll 32 and the pad 11. The other portion 42 of the pick-up is mounted on the butt face of the pad 11 of the roll and somewhat protrudes above its face, the head 41 of the screw 38 and the stationary portion 42 of the pick-up being equidistantly spaced from the center of the non-rotatable axle 33 of the rolling roll 32 (the designs of such noncontact pick-ups are known and disclosed in sufficient detail in technical literature).

The design of the roll stand in which the hollow rolls 32 having the bearing units 54 mounted therein and the nonrotatable axles 33 are used as idle rolls is advantageous in the cases when bars having a low yield limit are rolled and high rigidity of the parts of unit A of the roll stand is not required. In this event it is much easier to treat the frame 8 of the roll stand and to effect dynamic balancing of the idle hollow rolls 32.

The variant of embodiment of the roll stand with unit A shown in FIG. 4 has some differences as compared to the roll stand shown in FIG. 2, which reside in the following. I

The stator unit 16 is mounted on the side of the pad 10, that is external relative to the idle roll 15, and the casing 23 of the armature is mounted on the end portion 43 of the axle 20, in opposition to the stator winding 17, and is fixed with the aid of a nut 44.

This disposition of the parts of unit A allows to quickly set up the gap 28 between the surface of the stator winding and the surface of the armature due to free access to the parts of the roll stand.

Furthermore, thanks to the fact that the armature casing 23 is mounted on the end portion 43 of the axle 20 of the idle roll instead of being installed in the body of the roll, it is possible to decrease the width of the rolls 12, 14 and 15 and to dispose the bearing units 21 and 22 symmetrically with respect to the roll 15.

The roll stand of this design is compact and has a higher rigidity, whereas the rotatable parts can be easily subjected to dynamic balancing.

The roll stand functions as follows.

At the control board (not shown in the drawing) of v the rolling mill shown in FIG. 1 the operator makes all preparations necessary for switching-on all the electric circuits (not shown in the drawings): the circuit controlling the general controllable drive, the circuit effecting control over a.c. supply sources of the working frequency of more than 50 cps, and the circuit synchronizing the rates of rotation of the working roll and idle rolls. I-Iere use can be made of conventional electric circuits disclosed in special technical literature and suiting the specific conditions of the operation.

Then, the operator switches on the system cooling the stator windings 17 with the aid of the chambers 18 and the system cooling by compressed air the butt surface of the statorwinding 17 disposed in the annular gap 28. When there is liquid coolant in the coolingthe stator windings, controls it and set up the rate of rotation of each of the idle rolls 14 and 15 close to the rate of rotation of the working roll 12.

In order to eliminate the lagging behind of the rate of rotation of the idle rolls l4 and 15 with respect to the rate of rotation of the working roll 12, which takes place due to aerodynamic losses resulting from friction between the rolls 14 and 15 and air, losses resulting from friction in the bearing units 21, 22 and losses resulting from interaction of the idle rolls 14 and 15 with the water supplied into a groove to cool the latter, each of the roll stands 5 is provided with additional synchronization of the rate of rotation of the rolls 14 and 15 with the rate of rotation of the roll 12.

For this purpose the axle of each of the idle rolls l4 and 15 mounts the electric pick-ups 30 and 31 cut in the comparison circuit of the rates of rotation of the rolls and that of the working roll 12.

These circuits, in their turn, are connected through electric feed-backs to the control circuits of the supply sources so that in case of deviation of the rate of rotation of the idle'roll from the rate of rotation of the working roll, the frequency of the a.c. of the supply source is altered accordingly to change the rate of rotation of the idle roll.

At the moment a preset speed of rolling is set at the working roll 12, the synchronization of the rotation rates of the idle rolls 14 and 15 and that of the roll 12 Thereupon, the operator switches on the electric,

drive 1 and the supply sources of the stator windings, with the aid of the connecting clutch 2 the electric drive rotates the group reducing gear 3 which, in its turn, with the help of the output shafts 6 and the drive shafts 13 of the roll stands 5 starts rotating the working rolls 12, the electric pick-ups 7 disposed on the shanks of the output shafts 6 of the reducing gear 3 registering the rates of rotation of the working rolls 12.

The electric signals are delivered to the control electric circuits of the supply sources and comparison circuits of the rates of rotation of the working roll 12 and is completed too, and the rolling mill is ready for operation.

Then, metal bars are rolled in the mill in the direction as indicated by arrows in FIG. 1.

The operation of the roll stands with units A shown in FIGS. 3 and 4 is absolutely similar to the operation of the roll stand shown in FIG. 2 and employed in the rolling mill shown in FIG. 1. Y

A great advantage of the roll stand of the present invention lies in considerable increase of the speed of rolling and, consequently, an increased efficiency of the rolling mill.

The increase in the speed of rolling is achieved due to elimination of bevel gearings from the roll stand, the gripping angle remaining the same as in the case of employment of the latter.

Absence in the roll stand of bevel gearings used for distribution of rotation among rolls makes it possible to vary the diameter of the rolling rolls by selecting the most expedient from the technological point of view, diameter thereof and reduction ratio of the bar being rolled in the groove of the stand.

Employment in the present roll stand of the group reducing gear 3 of a simple design with cylindrical gearings also attributes to a higher speed of the rolling process in the roll stand.

Use in the roll stand of combined flange-type noncontact electric motors adapted to accelerate the idle rolls and synchronize the rates of rotation of the rolls with that of the working roll provides for a considerable decrease in the over-all dimensions of the roll stand, its weight, as well greater rigidity and strength of the stand.

The design of the present roll stand allows the provision of rolling equipment exhibiting high dynamic characteristics and making it possible to roll bars of a small cross-section at high speeds m/sec and higher).

Although being simple in design and small in size, the roll stand of the block-structure rolling mill possesses widest technological possibilities, as compared to any other block-structure stands.

What we claim is:

l. A roll stand of a block-structure mill for rolling solid and hollow metal bars, said roll stand comprising a frame having pads; bearing units being mounted into said pads and carrying axles, said axles having a working roll and at least one idle roll; drive means for deforming a bar being rolled-and being connected to said working roll; drives of said idle rolls, said drives being adapted to accelerate them and to synchronize the rate of their rotation with that of said working roll, each of said drives being made as a combined non-contact electric motor having an armature which is mounted on the axle of said idle roll and a stator being formed essentially as a winding mounted in said pad of said roll stand and being disposed in a plane parallel to the plane of rotation of the roll; and a.c. supply sources being connected to said stator windings of said combined noncontact electric motor, providing for a rotating magnetic field between said stator windings and armatures, said magnetic field by interacting with said armature mounted in said idle roll rotating the latter.

2. A roll stand as claimed in claim 1, wherein said stator windings are made as printed windings.

3. A roll stand as claimed in claim 2, wherein said armature of said non-contact electric motor is mounted on the butt face of said idle roll, facing the butt face of said pad mounting said stator winding.

4. A roll stand as claimed in claim 2, wherein said stator winding is mounted on the face of the pad that is external relative to said idle roll, and wherein said armature is mounted on the end portion of said axle of said idle roll in opposition to said stator winding.

5. A roll stand as claimed in claim 2, wherein in order to raise precision of synchronization of the rates of rotation of said idle rolls and that of said working roll, said axles of said idle rolls mount electric pick-ups of rotation rates, said pick-ups being cutin comparison circuits of the rates of rotation of said working roll and each of said idle rolls, said circuits being electrically connected to a.c. supply source so that when the rate of rotation is deviated from that of the working roll, the

frequency of said a.c. supply source is altered accordingly to change the rate of rotation of said idle roll.

6. A roll stand of a block-structure mill for rolling solid and hollow metal bars, said roll stand comprising a frame having pads; a working roll and at least one idle roll being disposed between said pads; bearing units of said working roll mounted in said pads and carrying an axle with a working roll; said idle rolls being made hollow and accommodating one bearing unit in each, said bearing unit carrying a non-rotatable axle of the roll; drive means for deforming a bar being rolled and connected to said working roll; drives of said idle rolls being adapted to accelerate the latter and to synchronize the rates of their rotation with that of the working roll, each of said drives being fashioned as a combined non-contact electric motor having an armature which is mounted on the butt face of said hollow idle roll and a stator being essentially formed as a winding mounted in said pad of said roll stand and being disposed in a plane parallel to the plane of rotation of the roll; and a.c. supply sources being connected to said stator windings of said combined non-contact electric motor, providing between said stator windings and armatures a rotating magnetic field which by interacting with said armature mounted in said idle roll rotates the latter.

7. A roll stand as claimed in claim 6, wherein in order to raise precision of synchronization of the rates of rotation of said idle rolls and that of said working roll, provision is made for non-contact pick-ups cut in comparison circuits of the rates of rotation of said working roll and each of said idle roll, said circuits being electrically connected to a.c. supply sources so that when the rate of rotation of the idle roll is deviated from that of said working roll, the frequency of the a.c. of the supply source is altered accordingly to change the rate of rotation of the idle roll, one portion of said pick-up being mounted on the butt face of said hollow roll and facing the other portion of the pick-up mounted on the butt face of said pad, both portions of the pick-up being equidistantly spaced from the center of said nonrotatable axle. 

1. A roll stand of a block-structure mill for rolling solid and hollow metal bars, said roll stand comprising a frame having pads; bearing units being mounted into said pads and carrying axles, said axles having a working roll and at least one idle roll; drive means for deforming a bar being rolled and being connected to said working roll; drives of said idle rolls, said drives being adapted to accelerate them and to synchronize the rate of their rotation with that of said working roll, each of said drives being made as a combined non-contact electric motor having an armature which is mounted on the axle of said idle roll and a stator being formed essentially as a winding mounted in said pad of said roll stand and being disposed in a plane parallel to the plane of rotation of the roll; and a.c. supply sources being connected to said stator windings of said combined non-contact electric motor, providing for a rotating magnetic field between said stator windings and armatures, said magnetic field by interacting with said armature mounted in said idle roll rotating the latter.
 2. A roll stand as claimed in claim 1, wherein said stator windings are made as printed windings.
 3. A roll stand as claimed in claim 2, wherein said armature of said non-contact electric motor is mounted on the butt face of said idle roll, facing the butt face of said pad mounting said stator winding.
 4. A roll stand as claimed in claim 2, wherein said stator winding is mounted on the face of the pad that is external relative to said idle roll, and wherein said armature is mounted on the end portion of said axle of said idle roll in opposition to said stator winding.
 5. A roll stand as claimed in claim 2, wherein in order to raise precision of synchronization of the rates of rotation of said idle rolls and that of said working roll, said axles of said idle rolls mount electric pick-ups of rotation rates, said pick-ups being cut in comparison circuits of the rates of rotation of said working roll and each of said idle rolls, said circuits being electrically connected to a.c. supply source so that when the rate of rotation is deviated from that of the working roll, the frequency of said a.c. supply source is altered accordingly to change the rate of rotation of said idle roll.
 6. A roll stand of a block-structure mill for rolling solid and hollow metal bars, said roll stand comprising a frame having pads; a working roll and at least one idle roll being disposed between said pads; bearing units of said working roll mounted in said pads and carrying an axle with a working roll; said idle rolls being made hollow and accommodating one bearing unit in each, said bearing unit carrying a non-rotatable axle of the roll; drive means for deforming a bar being rolled and connected to said working roll; drives of said idle rolls being adapted to accelerate the latter and to synchronize the rates of their rotation with that of the working roll, each of said drives being fashioned as a combined non-contact electric motor having an armature which is mounted on the butt face of said hollow idle roll and a stator being essentially formed as a winding mounted in said pad of said roll stand and being disposed in a plane parallel to the plane of rotation of the roll; and a.c. supply sources being connected to said stator windings of said combined non-contact electric motor, providing between said stator windings and armatures a rotating magnetic field which by interacting with said armature mounted in said idle roll rotates the latter.
 7. A roll stand as claimed in claim 6, wherein in order to raise precision of synchronization of the rates of rotation of said idle rolls and that of said working roll, provision is made for non-contact pick-ups cut in comparison circuits of the rates of rotation of said working roll and each of said idle roll, said circuits being electrically connected to a.c. supply sources so that when the rate of rotation of the idle roll is deviated from that of said working roll, the frequency of the a.c. of the supply source is altered accordingly to change the rate of rotation of the idle roll, one portion of said pick-up being mounted on the butt face of said hollow roll and facing the other portion of the pick-up mounted on the butt face of said pad, both portions of the pick-up being equidistantly spaced from the center of said non-rotatable axle. 